1. Field of the Invention
This invention relates to a printing machine for controlling an ink feeding rate by measuring the color density of prints produced.
2. Description of the Related Art
Such a printing machine includes ink feeders for adjusting the rates of feeding inks to ink rollers. Each ink feeder has a plurality of ink keys juxtaposed in a direction perpendicular to a printing direction (i.e. a direction for transporting printing paper at printing time). Each ink feeder adjusts the rate of feeding ink to the ink rollers by varying the opening degree of each ink key. In this way, the rate of feeding ink ultimately to a printing plate is adjusted. For manually adjusting the opening degree of each ink key, a construction is provided for operating key control switches displayed on a control panel and corresponding to the ink keys, respectively.
The ink keys, 10 to 20 in number, are arranged in the direction perpendicular to the printing direction. It is difficult to correlate the key control switches corresponding to these ink keys with an image actually being printed.
It is thus conceivable to use a control panel such as a touch panel (also called a touch sensitive screen) for displaying the key control switches as well as an image actually being printed. However, where the control panel has a limited display space (area), it is difficult to display simultaneously the key control switches and the image actually being printed.